The ESP32, An SDR In Itself

What happened

Perhaps the most famous of all the software-defined radio (SDR) receivers is the RTL-SDR, a digital TV receiver on which an undocumented feature was found. The undocumented mode can be found on ESP32 chips with the earlier Tensilica hardware onwards, so the low power Bluetooth only chips or the non-radio-equipped P4 won’t work.

Sadly it’s also only possible with the receive side, with both 2.4 and 5 GHz bands being supported depending on the microcontroller in question. It seems in the case of some members of the ESP32 family, they do. It’s a discovery made independently in two places, by Espargos , and a Reddit user by the name of h0m3us3r .

Key facts

• The undocumented mode can be — found: on ESP32 chips with the earlier Tensilica hardware onwards, so the low power Bluetooth only chips or the non-radio-equipped P4 won’t work